Note: Descriptions are shown in the official language in which they were submitted.
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1 TRAILER LANDING GEAR CUSHION FOOT
BACKGROUND OF THE INVENTION
This invention relates to a cushion foot assembly
for a trailer landing gear support.
Cushioned feet for landing gears have been
generally known for some years. Epstein 3,219,362 proposed
the use of resilient blocks between upper and lower plates
that were bolted together. The upper plate was bolted to a
frustum welded on the lower end of the landing gear leg.
Dalton et al 3,666,190 inserted a resilient toroid between
the leg and the foot, the latter being crimped onto or
bolted onto the leg. Dreyer et al 4,462,612 retained the
foot with crimping onto the leg portion, holding an elastic
pressure body in place. Ringe 4,634,144 crimped the foot
over the leg to retain a wedge-shaped resilient member.
Baxter 4,824,136 bolted the foot to the leg, with a
resilient pad enclosed therebetween. It will be noted that
all of these except the Epstein proposal enclose the pad so
that it is not visible to evaluate its condition or
potential replacement. Most of them, moreover, do not have
the foot readily removable from the leg for replacement in
case of damage to the foot. Such damage can readily occur,
for example, if the trailer supported on a landing gear
shifts, or the landing gear foot is lowered onto an uneven
surface as on a rock, or a partially elevated foot strikes
something during movement of the trailer. The typical
marketed landing gear foot of the padded type has a
fore-to-aft articulation of about five degrees, and a
side-to-side articulation of about five degrees, such that
placement on an uneven surface more than this angle can
readily damage the foot and/or leg structure under the heavy
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1 load of the trailer. Replacement of deteriorated rubber
pads is a problem with these prior units as can be readily
envisioned. Rubber pads do deteriorate as by entry of mud,
dirt, etc. into the housing, and by aging of the rubber, so
that they should be periodically replaced. Damage to the
foot also calls for replacement. Removal of the foot too
often requires use of a cutting torch, followed by the
problem of mounting another foot on the leg or alternatively
replacement of the entire leg. These actions require
specially trained repairmen. While the foot of the support
in patent 4,634,144 can be removed for replacement, it only
- fits on the special leg as there shown.
- An object of this disclosure is to provide an
effective cushioned landing gear foot which allows ready
visibility of the resilient cushion to enable evaluation of
the conditlon thereof, and which enables the foot to be
readily removed for replacement of the rubber cushion or to
substitute another foot in the event of damage to the
existing one. The replacement can be made without having to
use a cutting torch, but simply by knocking out a clinch pin
in the suspension axle. The housing for the axle is below
the leg and also serves as an abutment to engage the
cushion.
The foot is attached to the leg by a tubular
suspension axle which is arranged such that it does not have
any initial compression load applied to it when the landing
gear is lowered to support a trailer. The lower end of the
leg has an abutment member which engages the resilient pad
under compression load. The member has a rectangular cross
section including a flat bottom surface for abutting the
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pad. The pad has sufficient clearance with respect to a pair of
fore-and-aft inverted L-shaped retaining walls to allow an
approximately 20 degree fore-and-aft articulation of the foot on
the leg, and an approximately five degree side-to-side
articulation. The clearance between this flat surface (in
elevated condition) and the resilient pad is less than the
potential vertical movement of the hollow suspension axle in a
pair of slots into which it extends, so that when the landing
gear is lowered, the abutment member first engages the pad and
compresses it without the suspension axle being put into
compressive load. When the resilient pad is resiliently
distorted under a load on the assembly approaching a
predetermined partial load, preferably about 15,000 to 20,000
pounds, the axle begins to bear some load. When the load on the
pad exceeds a predetermined maximum, preferably no more than
about 25,000 pounds, the axle bears all of the excess load.
Embodiments of the invention will now be described
with reference to the accompanying drawings wherein:
Fig. 1 is a side elevational view of a landing gear
assembly embodying the invention;
Fig. 2 is a rear elevational view of one of the
landing gear leg and foot assemblies of the landing gear
mechanism;
Fig. 3 is an enlarged side elevational view of the
novel components at the lower end of the landing gear leg and
cooperative foot embodying this invention;
Fig. 4 is a side elevational view of the components
in Fig. 3 showing the fore-to-aft articulation range;
Fig. 5 is a rear elevational view of the
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'
- 1 components in Figs. 3 and 4, showing side-to-side
articulation;
Fig. 6 is a plan view of the resllient
compressible cushion or pad embodying this invention; and
Fig. 7 is an end elevational view of the cushion
- in ~ig. 6.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now specifically to the drawings, the
landing gear assembly 10 typically comprises a pair of like
landing gear legs, a gear box adjacent one of these legs, an
input drive shaft to the gear box for engagement with a hand
crank, and a cross shaft to the second leg. The combination
will be described herein relative to one leg assembly, it
being understood that the novel features on the second leg
lS assembly are identical.
More specifically, referrlng to the drawings, the
single leg assembly 12 of the landing gear assembly 10 is
shown to include a telescopic leg employing an upper outer
tubular leg member 14 and a lower inner tubular leg member
16. Each leg assembly is extendable and contractible by a
screw mechanism comparable to that, for example, set forth
in U.S. Patent 3,518,890, such that when the telescopic leg
is vertically extended, it can support a trailer on the foot
mechanism, and when retracted upwardly can be suspended
beneath a semi-trailer or the like. Operation of the screw
mechanism is through a conventional gear box 20 actuated as
by a crank (not shown) through an input shaft 22. An output
shaft 26 can connect to a cross shaft (not shown) to the
second leg (not shown) in conventional fashion.
The lower outer end of inner tubular leg 16 has a
plate 18 affixed thereto as by welding. Beneath this plate
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1 and welded thereto is a tubular abutment member 26 elongated
transversely relative to the vehicle direction of movement.
As shown, it is rectangular in cross sectional configura-
tion, preferably square. It has an inner width and height
just larger than the outer diameter of the axle it receives,
and a length less than that of the axle, so that the axle
ends protrude therefrom. This hollow abutment member also
serves as a housing for an elongated tubular axle 32
extending through the abutment housing. Suspended from the
ends of axle 32 is a foot subassembly 40.
This foot subassembly 40 includes a ground
engaging base plate 42 having a pair of spaced side flanges
44 extending upwardly therefrom and made integral therewith
as by welding. The lower ends of plates 44 preferably
extend outwardly diagonally, as shown, for reinforcement.
These side plates 44 have horizontally aligned orifices,
each of vertical slot-type configuration. The width of the
orifices is slightly larger than the outer diameter of axle
32 and the height considerably greater than the diameter of
axle 32 to allow vertical "play" movement of this axle.
When the foot is suspended by an elevated leg, the dimension
by which these orifices 48 is vertically longer than the
diameter of axle 32 is significantly greater than the
vertical clearance between the lower abutment surface of
abutment housing 26 and the top of the underlying resilient
pad 50 to be described. This is for purposes hereinafter
noted. The bottom surface of abutment housing 26 is flat,
the corner portions being radiused as depicted in Figs. 3
and 4. When the landing gear leg is elevated, shoe 40 is
suspended on axle 32 via side plates 44, the axle resting
against the inside bottom surface of abutment housing 26.
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1 Side plates 44 form two parallel walls of a pocket
at the upper surface of base plate 42 of foot 40. The
fore-and-aft walls of this pocket are defined by a pair of
inverted L-shaped plates 52 of a height preferably somewhat
greater than the height of resilient pad 50. The upper
outwardly extending flanges of these inverted L-shaped
plates have been found highly effective in providing the
strength necessary to resist deformation thereof when the
resilient pad is under compression due to the weight of a
loaded trailer. Specifically, the structure can accommodate
a load even up to 100,000 pounds, although using a hollow
housing. This is in contrast to prior landing gear devices.
Resilient cushion 50 has an at rest configuration
basically like that depicted in Figs. 6 and 7. More
specifically, it comprises a generally rectangular rubber
member approximately twice as long in its transverse
dimension, i.e., crosswise of the trailer to be supported,
than in its fore-to-aft dimension. The side walls 50' are
tapered upwardly inwardly, especially at the front and rear
walls thereof. The resilient pad is retained in its pocket
by a friction fit achieved with four small protrusions 50a
extending forwardly and rearwardly, to be deformed when the
pad is pressed into position. Preferably, the front and
rear walls of the pad also have central notches 50b, and
there is a tapered orifice 50c in the center of both ends
thereof. The tapered walls 50', notches 50b and tapered
orifices 50c enable temporary rubber position transfer
laterally when the unit is under vertical load.
Axle 32 is held in abutment housing 26 by locking
pins 60 extending through orifices 32' through the opposite
ends of the axle extending beyond the ends of housing 26.
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1 Drain holes in the foot at the bottom of the pad allow water
to drain out of the pocket.
When the telescopic leg is vertically extended and
put under load, this load is not initially applied to axle
32 since the clearance between the bottom surface of
abutment housing 26 and the top of pad 50 is significantly
less than the clearance between the outer diameter of axle
32 and the top of slot orifices 48. Application of the full
load to abutment 26 causes it to depress into the resilient
pad, forcing portions of the rubber pad laterally outwardly
into the clearances fore-and-aft of abutment 26, i.e.,
between it and fore-and-aft support walls 52 (Fig. 3). This
condition is shown somewhat exaggerated in Fig. 3. As load
is progressively increased on the assembly, by cranking down
of the inner leg and the attached foot, some of the load
begins to be applied to axle 32 because the pad is then
sufficiently deformed to cause axle 32 to approach the
bottom ends of slots 48. This preferably begins to occur
when the load applied is a predetermined amount preferably
in the amount of about 15,000 to 20,000 pounds applied to
each leg, i.e., 30,000 to 40,000 pounds on both legs. As
the load exceeds about 25,000 pounds per leg, the axle bears
all of the excess load above the predetermined maximum load,
i.e., preferably about the 25,000 pound amount, with the
resilient pad still bearing the remaining 25,000 pound load,
but no more. This controlled loading is achieved by
selecting the difference between the clearance of abutment
26 from the top of pad 50, and axle 32 from the bottom of
slots 48.
It has been found that the polygonal configuration
of the abutment housing, particularly the square cross
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1 sectional configuration as illustrated, resists deformation
under the inward pressure of the resilient material against
the walls thereof under load conditions better than a
cylindrical housing of circular cross sectional
configuration. In the illustrated embodiment, the distance
front to rear between the inner surfaces of fore-and-aft
support walls 52 is three inches, while the front to rear
outer dimension of housing abutment 26 is two and one-half
inches, thereby leaving approximately a one-quarter inch
clearance at the front and at the rear. Further, the taper
on the edges of the one inch thick pad is approximately
one-quarter inch across on each of the front and rear sides
thereof. The wall taper is offset, therefore, about 25
percent of the pad height, for an angle of taper of about 22
1/2 degrees. These combined features enable up to about 20
degrees articulation fore-to-aft of the foot relative to the
leg as depicted in Fig. 4. Yet the structure has fully
adequate support in such condition for heavy loads. The
rubber pad is preferably an SBR (styrene-butadiene
copolymer), such as SAE J200 5AA 725A13B13F17. Other
suitable resilient elastic materials, preferably rubber, can
be employed, such as GR-S or Buna-S. The side clearance
between the ends of abutment housing 26 and side plates 44
is relatively small, permitting articulation side-to-side of
up to about five degrees.
The exposed rubber cushion can be readily visually
observed to determine its condition. If the resilient
member deteriorates and/or the foot of the structure is
damaged, the foot can be quickly removed for replacement of
the pad and/or replacement of the entire foot subassembly.
More specifically, one or both clinch pins 60 extending
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1 through orifices 32' (Fig. 5) in the ends of axle 32 can be
driven out as by a punch, allowing axle 32 to be removed,
thereby dropping foot subassembly 40 from the leg for
replacement of the pad and/or foot. The new one is
installed simply by inserting the axle back into position
and driving in a new locking pin.
Those in the art, upon studying this disclosure
and the detailed description of the preferred embodiment,
will likely envision variations within the concept
presented. Thus, the invention is intended to be limited
only by the appended claims and the reasonable equivalents
to that defined therein.
